For correct diagnosis of various cancer diseases biopsies are taken. This can either be via a lumen of an endoscope or via needle biopsies. An example of a needle biopsy is shown in FIG. 7, where a biopsy is taken from the prostate via the rectum. In order to find the correct position to take the biopsy, various imaging modalities are used such as X-ray, MRI and ultrasound. In case of prostate cancer in most cases the biopsy is guided by ultrasound (see FIG. 7). Although helpful, these methods of guidance are far from optimal. The resolution is limited and, furthermore, these imaging modalities can in most cases not discriminate between benign and malignant tissue. As a result we do not know for certain whether from the correct part of the tissue a biopsy is taken. We take almost blind biopsies and even if after inspection of the tissue no cancer cells are detected, we do not know for certain that we did not simply miss the right spot to take the biopsy.
In order to improve the biopsy procedure direct inspection of the biopt position prior of taken the biopt is required. A way to achieve this is by microscopic inspection at this position. This requires a miniaturized confocal microscope. In the publication in Optical Fibers and Sensors for Medical Diagnosis and Treatment Applications, Ed. I Gannot, Proc. SPIE vol. 6083 the article “A full-color scanning fiber endoscope”, by E. J. Seibel et al., a fiber scanning fiber endoscope (see FIG. 8) a fiber scanning system based on a piezo actuator is described. A drawback of this system is that it is operated in a resonant way. Apart from being fast, a resonant scanner has two drawbacks. The first is that scanning pattern is fixed (see FIG. 9). If a certain part of the image is of interest only or if you want to measure at a fixed position you always have to scan the complete object. Especially in the case of spectral imaging and two-photon spectral imaging some time is required to collect the photons to have sufficient statistics. Also the needed relatively high voltage of ˜75 Volt poses additional constraints for, e.g., an endoscope or catheter.
Another drawback is that, due to resonance mode, the position of the end tip of the fiber depends strongly on the properties of the fiber. Small differences in the manufacturing of the fiber will affect the scanning properties. Another drawback is that the deflection of the fiber tip is limited in case of resonant scanning The longer the fiber the slower the scanning and the larger the fiber part beyond the actuating device. A longer fiber makes the system tolerance sensitive and the risk of other modes than the resonant mode is high. This means that resonant scanning is less preferred.
In U.S. Pat. Nos. 6,967,772 and 7,010,978, a scanning fiber system is described based on an electrically operated tuning fork. Again this system is operated in resonance mode with some of the drawbacks as mentioned above. Furthermore, the tuning fork makes the system rather bulky limiting the downscaling of the system.
In U.S. Pat. No. 7,123,790, a scanning fiber system is described using four electrical coils with windings in a plane perpendicular to the fiber. The system of U.S. Pat. No. 7,123,790 uses a resonant driving method for scanning the fiber tip in an elliptical pattern.
It is a disadvantage of the above described fiber scanning systems, that they employ resonance scanning of the fiber resulting in a system in which the area to be scanned cannot be easily adjusted and in which the position of the fiber tip is less well-defined.
In U.S. Pat. No. 5,317,148, a permanent magnet, attached to an optical fiber, is enclosed by two electromagnet pairs with windings in a plane parallel to the fiber. By controlling the voltage to each of the magnets, the exact position of the permanent magnet is controlled. As a result, the position of the free end of the optical fiber is controlled to scan a target area using various patterns. It is a disadvantage of the system disclosed in U.S. Pat. No. 5,317,148 that it is relatively large and that is not suitable for miniaturization. For example, for medical applications miniaturization is an important aspect in order to minimize tissue damage during examination of the patient.